The Natural (non-invasive) Erection Test: Is it a reliable alternative to the artificial erection test?

To test the accuracy and reliability of the natural erection test (NET) as compared to the artificial erection test in assessing penile curvature in hypospadias.

50 children underwent both natural and artificial erection tests intraoperatively between January 2020 and October 2021. These included 5 glandular, 26 distal, 9 proximal, and 10 perineal hypospadias patients with curvature. The mean follow up period was 20 months (range 16-37). Under anesthesia, the curvature was assessed before degloving, then after degloving using both the natural and the artificial erection test. The NET test was repeated after curvature correction (3 times per patient). The measurements were analyzed using paired t-test.

Two fingers of the left hand press just below the symphysis pubis to stop blood drainage from the penis and two fingers of the right hand massage the blood from the perineum distally into the penis until it becomes hard without tourniquet. The standard artificial erection test was performed using saline injected through a butterfly needle into the corporeal bodies without tourniquet. Photos were taken of both tests using the exact angle and angle of curvature was measured using Angle Meter App.

There was no statistically significant difference between both erection tests with a P value of 0.705. The Bland-Altman plot also showed that all studied children have a difference in their natural and artificial erection tests within the limits of agreements.

Erection is commonly induced using the artificial saline injected erection test first described by Gittes and less commonly using pharmaceutical erection test first described by Perovic. The severity of chordee apparent during artificial erection test varies with the amount of pressure used during injection. Also, it is difficult to place the tourniquet proximal enough to detect chordee at the base of the penis. It may be associated with hematoma formation, oedema, postoperative pain and the need for multiple punctures to assess the curvature before and after repair. Disadvantages of the pharmacological-induced erections in hypospadias include increased blood loss during erection, additional cost, and the need for a reversal agent. The natural erection test mimic the normal erection mechanism and may avoid all these potential disadvantages.

The study showed that the natural erection test is easy to perform, non-invasive, non-traumatic and can be repeated several times intraoperatively without the need of repeated puncturing of the corpora cavernosa and avoids the potential risks and complications of the artificial erection test.